The invention pertains to a lifting mechanisms for typewriter ink ribbons and correction tapes. More particularly, the invention pertains to a system for raising and lowering separate typewriter ink ribbons and correction tapes.
Generally, two types of ink ribbons are used for typewriters. One is a multi-strike fabric ribbon and the other is a one-time or one-strike ribbon.
The ink-hydrous type of fabric ribbon is formed on a ring and is arranged to be struck repeatedly at substantially the same spot. However, due to its fabric construction, the printing quality of the fabric ribbon is generally not high.
On the other hand, a one-time or one-strike ribbon which is generally made of plastic, is arranged not to be struck at the same spot again because, otherwise, plastic film at the tape surface would be scaled-off. Therefore, the feeding pitch of the one-time or one-strike ribbon is desirably arranged to be as short as possible yet non-overlapping.
Referring to FIG. 2 and FIG. 3, the width d of the illustrated ribbons are sized four to five times the size of the print character. As the ribbons are fed in the direction of the arrows, the ribbon is simultaneously lifted and lowered per each printing action. Accordingly, since the striking position moves up and down, overlapped printing is avoided although the feeding pitch may be very small.
The use of overlap avoidance for a single strike ribbon is explained by way of reference to FIG. 2. For instance, when "A" is to be printed, it is printed in order of P.sub.1 -P.sub.2 -P.sub.3 -P.sub.4 . . . . Overlapped printing is avoided as the striking position moves up and down.
The use of overlap avoidance for a multi-strike ribbon is explained by way of reference to FIG. 3. The feeding pitch illustrated in FIG. 3 is smaller than the pitch of FIG. 2 and the characters are printed in the order of P.sub.1 -P.sub.2 -P.sub.3 -P.sub.4 -P.sub.5 . . . . In this example, although the striking position moves up and down, printing is also slightly overlapped, as the figure shows.
Accordingly, multi-strike ribbons generally have a longer useful life, but their printing quality is generally lower than the single-strike ribbons.
The above described ribbons are used for printing. Additionally, many typewriters provide for the use of a correction tape which corrects misprinted characters. In such systems, it is necessary to arrange lifting methods for both the ink-ribbon and the correction tape.
FIG. 1 shows an example of a prior known ribbon lifting apparatus. Referring to FIG. 1, item 1 denotes a driving shaft of a stepper motor M.sub.1. Item 2 denotes a pair of ribbon lift arms fixed to the driving shaft 1. The extended end portions of ribbon lift arms 2 include ribbon guides 2a which hold and direct an ink ribbon 3.
Item 4 represents a solenoid which lifts and lowers a link 5. Through the motion of the link 5, a pair of correction tape lift arms 6 are rotated around a fixed shaft 7 and thus the correction tape 8, held by the tape guides 6a, may be lifted or lowered. The fixed shaft 7 is fixed to typewriter body which is not shown in FIG. 1.
Under the above described lifting construction, printing is performed in the up and down order of P.sub.1 -P.sub.2 -P.sub.3 . . . (see FIGS. 2 and 3).
During printing using the known apparatus according to FIG. 1, the ribbon lift arm 6 is generally arranged to resume its original print position after each printing action. An exception to this is provided in certain typewriters wherein a printing REPEAT function is allowed.
During correction operation, on the other hand, the solenoid 4 lifts up the tape lift arm 6 through the link 5 whereby the correction tape 8 is oriented in the correct position to be struck.
In the above described known lifting mechanism (FIG. 1), the printing ribbon 3 is lifted by the stepper motor M, and the correction tape is lifted by the solenoid 4. Thus, two drivers are needed to perform the lifting functions. Such plural mechanisms result in higher cost and weight factors. Further, such mechanisms require accurately and minutely stepped stepper motors to effectively use multi-strike ribbons; such stepper motors are expensive and of a bulky size.
It is therefore an object of the invention to provide an effective and efficient print ribbon and correction tape lifting mechanism.
It is a further object of the invention to provide a print ribbon and correction tape lifting mechanism which is low in cost while being effective for both single strike and multi-strike ribbon applications.